The present invention relates to an adaptive equalizer for use in a high definition television (HDTV) receiver, and more particularly to an apparatus and a method for controlling the operation of the adaptive equalizer which is capable of reducing interference of a signal due to a multi-path or fading phenomenon in a channel.
In general, a high definition television receiver is known as a next generation television system which has picture quality being on the same level as that of 35 millimeter cinema film, and tone quality being on the same level as that of a compact disc. The high definition television receiver includes an adaptive equalizer for normally regenerating a received signal that has been degraded by multi-path or fading phenomenon occurring within a broadcasting channel over which the signal is transmitted. Such an adaptive equalizer is comprised of a filter having finite impulse response (FIR) characteristic in order to compensate for degradation of the receiving signal due to transmission over the digital communication system channel.
Typically, a telephone line modem is representative of a system employing a known adaptive equalizer. In this case, the data transmission rate is about 2400 sps (symbol per second). However, the known adaptive equalizer cannot be used in a high definition television system which digitally processes all received signals, because the high definition television system requires a data transmission rate of about 5 Msps. Therefore, it is necessary to provide an apparatus and a method for controlling the real time operation of a high definition television adaptive equalizer in order for it to perform at a high rate of transmission speed. In order to compensate for the multi-path and the fading phenomenon generated within the transmission channel, the length of the multi-path error, controllable in the adaptive equalizer, differs according to the length of a FIR filter and equalization algorithm. However, the length should generally be between a corresponding delay of -2 .mu.s and +24 .mu.s. In this case, the number of taps in an adjustable filter is about 100 to 256. When the HDTV receiver initially operates, the effects of all multi-path signals to a corresponding delay of between -2 .mu.s to +24 .mu.s are equalized by an adaptive equalizer, however, this requires a long initialization time. Moreover, according to the state of the art of current digital signal processing techniques, it is very difficult to obtain, in real time, approximately 100 to 256 coefficients from a single input symbol where the received signal has a data transmission rate of about 5 Msps. Therefore, a HDTV receiver adaptive equalizer must have a short waiting period until the recovered video and audio signals are available. Accordingly, solutions are needed to minimize the waiting period.